Continuous metal srip casting plant

ABSTRACT

A continuous metal strip casting plant on which is mounted, at the casting location, a mobile ingot mould comprising two cylindrical metallic casting rolls in addition to other components, amongst which there are a tundish and/or under tundish and/or an unloader and/or lateral plates, respective preheating stations located in positions separated from the position of casting, and rotating arms located on a turret itself also placed on the casting plane to transfer the components from the casting line to their preheating stations.

FIELD OF THE INVENTION

The present invention relates to a plant for continuous casting of metalstrip and more precisely it relates to a plant provided with automatedmeans for assembling or replacing some of its parts.

STATE OF THE ART

Since some time the possibility has arisen of carrying out thecontinuous casting of metals directly in the shape of strips ofindefinite length, only depending on the amount of molten metal both tobe cast and actually cast, essentially with the aim of overcoming thetechnical, economic and environmental drawbacks associated with thecasting of ingots or slabs of considerable thickness to be latertransformed by means of hot and possibly cold lamination operations intostrips having thicknesses ranging from a few millimetres (hot strips) toa few tens of millimetres (cold strips). Already used for some decadeswith the treatment of metals such as copper and aluminium, thecontinuous casting of metallic strips has been proposed for materialswith high smelting points, in particular firstly for stainless steel andlow carbon content steel and then for steels with high surface qualityrequirements such as stainless steels, with silicon for magnetic uses,etc. However, at the moment, technology is still at a pilot plant stagefor these materials, due to the several difficulties, especiallyassociated with the high smelting temperatures of said ferrous materialsand to their relatively slow solidification, and the need to combine thecharacteristics of a strongly innovative process with the structure ofmore traditional collateral plants. For example, a problem stillunresolved is that of guaranteeing the continuity of the process, inparticular in view of the replacement of parts of the plant. In fact, asin many industrial processes also in the continuous casting of metallicstrip the possibility of operating really continuously ensures notabletechnical and economical advantages. In this respect, it is extremelyimportant to succeed in substituting, in the least amount of timepossible, any component of the plant, i.e. both of the casting machineitself (groups containing the casting rolls which make up the ingotmould) and the refractory components (tundish, under-tundish, sideplates, unload nozzle).

For example, in EP-A-450775 a continuous casting plant of a strip, alsodenominated “strip casting” from the English technical terminology, isdescribed, in which the cooled casting rolls constituting the ingotmould are mounted on a mobile trolley on rails between a first mountingand standby station and a second casting station. The other components,such as the tundish and unloader, are heated in ovens arranged nearbythe casting plane and transported to the mobile trolley suspended from abridge crane.

EP-A-947261 describes a “strip casting” plant in which the cooled rollsconstituting the ingot mould are mounted on a mobile trolley between afirst position, below the casting plane, and a second position on thecasting plane. This document describes the means for mounting the rollson the trolley and the means for adjusting them; no details on the othercomponents are given, such as the tundish and the unloader, inparticular regarding their preheating and their transportation from theheating station to that of the casting.

The Japanese published patent application JP-A-6-335753 describes a“strip casting” plant in which the rolls constituting the ingot mouldare changed, in case of necessity, by means of a bridge crane.

In summary, in the previous technical literature examined are used, nextto a sophisticated plant at very high productivity such as that of“strip casting”, traditional machinery such as bridge cranes whichrequire manual interventions for the attachment and detachment of thecomponents to transport and present somewhat long completion times.

DESCRIPTION OF THE INVENTION

According to the present invention, a continuous casting plant of ametallic strip is disclosed, said casting plant comprising a castingplane, a casting station and a plurality of further stationssubstantially separated from said casting station and, in said castingstation, a mobile ingot mould comprising two cylindrical, cooled,counter-rotating rolls and two plates each of which is set at the endsof said rolls, to close at the sides of said rolls the space betweenthem, said rolls defining, between their respective facing surfaces, aspace inside which molten metal is cast and solidifies upon contact withthe surface of said rolls and is then extracted from below as a hotmetal strip, and said continuous casting plant further comprising aplurality of further component elements, treatment stations for saidadditional component elements, and moving means for moving each of saidadditional component elements, wherein said treatment stations are allset on the casting plane, said further component elements being movedbetween their respective treatment stations and said casting station byrotating arms located on at least one turret, said turret being set onthe casting plane.

Preferred embodiments provide for two of such turrets each of whichbeing located close to one side of the casting station.

Two additional minor turrets are placed alongside the casting station,parallel with the vertical casting plane.

Said additional component elements moved by rotating arms are: a ladle,at least one tundish and/or at least one under-tundish, and/or at leastone molten metal distributor within said space between counter-rotatingrolls, and/or the two side plates which rest at the flat ends of saidrolls, to laterally close the space between the rolls.

Said turrets are each provided with two arms, one suitable to move thetundish and the other one suitable to move the under-tundish from therespective treatment stations (maintenance, preheating, . . . ),arranged near to the turrets within the reach of said arms, and thecasting station.

The additional turrets carry robotic arms for moving said molten metaldistributor, and said lateral plates of the respective treatmentstations (maintenance, preheating, . . . ) to the casting station; theyare located nearby the casting station, on a plane parallel to thatcontaining the cast strip.

The casting rolls are arranged within a trolley which can movetrasversally to the direction of casting between a treatment position(maintenance, mounting, regulation, . . . ) and the casting station,said trolley being provided with means to set and hold in position therolls and to regulate their gap with the aim of controlling thethickness of the cast strip. The motor necessary to set the rolls inrotation during casting is fixed on the casting plane and isautomatically coupled to the system located on the trolley for thesynchronous rotation of the rolls.

The casting plane is also provided with a rail, parallel to the axis ofrotation of the rolls, on which said trolley moves between the castingstation and a treatment station for the rolls (maintenance, mounting onthe trolley, adjusting the mutual positions, . . . ).

The casting plane also carries a tower (ladle tower) to put the ladle inthe casting station, preferably arranged in a central position withrespect to the turret for the movement of the tundish and under-tundish.

On the casting plane means for collecting wastes of slag and of metaland means for movement thereof are also provided.

A preferred mode of working of said plant is described herein asfollows. At the start of the casting process, tundish and under-tundish,metal distributor and side plates are all in their respective preheatingpositions near to the turrets for their moving. The casting rolls,arranged on a mobile trolley, are in their treatment station, whichcomprises means for moving the trolley from the position of mounting ofthe rolls to a standby position. Such means of movement can consist of acarriage containing two trolleys, one ready to be sent to the castingstation and the other waiting to be sent to the position for mountingand adjusting the rolls. In the meantime molten metal is loaded into theladle, which is transported nearby the ladle tower, held by anappropriate arm of the latter and carried to the casting station.Contemporarily, the tundish and possibly the under-tundish, for theplants in which this is envisaged, are set in their positions in thecasting station, each moved by one of the arms of said tundish rotatingtowers; it is to note that for greater flexibility of use and toovercome possible mechanical inconveniences, the tundish andunder-tundish to be placed in the casting station can be moved by therespective arms of the same turret or a tundish by one turret and anunder-tundish by another. Whilst the tundish is being filled with moltenmetal from the ladle, first the distributor and then the containmentplates are brought to the casting station. Immediately afterwards, it ispossible to begin the casting.

In such a way, it is possible to realise the simultaneous movement ofmany of the above described components from the respective preheatingstations to the respective casting station, significantly reducing theaccumulated time of setting in motion, or however of the movement of anyone of said components in the case of replacement during the executionof the casting.

In purely indicative and non limiting terms, one can say that during thesimulation of functioning, transfer times of the unloader and sideplates of even less than a minute have been obtained, whilst fortundishes and under-tundishes maximum times of less than three minuteshave been obtained, whilst for the casting rolls, mounted on thesupporting trolley, it has never been above five minutes.

DESCRIPTION OF THE DRAWINGS

The present invention will now be described in relation to the encloseddrawings, in which a possible embodiment of the same is shown by way ofa non-limiting example of the objects and scope of the invention.

FIG. 1 shows schematically a partially sectional side view of a plantaccording to the present invention.

FIG. 2 schematically shows a plan view of the plant of FIG. 1.

In FIG. 1, a ladle 1 is shown in working position and communicating witha tundish 3 through an unloader 2; from the tundish 3 the molten metalpasses, with a flow controlled by the rod 4, or through a slide gate orslide valve or other equivalent device, through the chamber 5, whichprotects the metal cast from oxidation, within an optionalunder-tundish, not shown, or directly into a distributor 7. Obviously,the plug rod can be replaced with other suitable means, for example asliding gate nozzle ladle. In the embodiment not provided with theunder-tundish, the molten metal which flows inside the distributorunloader 7 is distributed within the space existing between the tworolls 8, 8′, arranged in the container trolley 9 sliding on rails. Thetrace of the strip 15 leaving the ingot mould is shown. As can be seen,the tundish 3 is supported by an arm 12 of a tundish rotating turret 10,the other arm of which 11 holds the under-tundish 6. On the castingplane 16 a mechanical robotic arm 13 is also arranged which moves thedistributor unloader 7, and side plates of known type, and not shown inthe figures, from the respective heating positions to the castingpositions.

Now referring to FIG. 2, the distribution on the casting plane of thevarious parts of the plant can be better appreciated. In particular itcan be seen how the ladle turret 17 has two arms in line, one of whichcarries the ladle 1 to the casting station 25, whilst the other arm holda ladle 1′ in standby. The turret 10 has an arm 12 which in its turnsupports a tundish, not shown in this plan view, in the casting station,whilst the other arm 11 supports the under-tundish 6 heating in thestation 21. A second tundish rotating turret 10′ has in its turn an arm12′ supporting the tundish 3′ which is heated in the station 21′, whilstthe other arm 11′ holds an under-tundish (not shown) in the castingstation. Adjacent to the casting station 25, in which the mobile trolley9 is situated holding the rolls 8 therein. The rotation of said rolls isdriven by the motorised assembly 19—the heating ovens 18 and 18′ for theunloader and side plates are positioned, which are movable betweenheating positions and casting station by means of the relative roboticarms 13 and 13′.

The trolley 9 moves along the rails 14 between the casting station andits treatment station 20, in which a second trolley 9′ is placed, instandby. The changeover between the trolleys can take place, as shown inFIG. 2, by means of a carriage 24 holding both the trolleys 9 and 9′,and moving perpendicularly to the rails 14 between position 22 and thestation 20. The trolley 9, arriving from the casting station 25, ispositioned on the carriage, next to the trolley 9′ which is found inposition 22. The carriage 24 is then moved to put the trolley 9 in thestation 20 and the trolley 9′ on the rails. The carriage 24, at thispoint, is lowered, bringing the trolley 9′ on the rails 14 anddepositing the other trolley in the station 20. After that, the trolley9′ is sent to the casting station.

It is possible to use other methods for the changeover of the trolleys 9and 9′ in the casting station 25. For example, it is possible to locate,around the casting rolls treatment station 20, two couples of railswhich lead by a suitable junction to the rails 14, so that the twotrolleys 9 ad 9′ can move independently, so that as soon as one of thetrolleys is moved from the casting station to the treatment station onthe first of said couple of rails, the other trolley can immediatelymove in starting from the second couple of rails.

The movement of all the components is automated, there is no need tointervene manually to attach or fix the moving parts and the mostimportant and delicate parts move with simple rotational swingingmovements. The movements are therefore easily executable in a reallyshort time.

1. A continuous casting plant of a metallic strip comprising a castingplane, a casting station and a plurality of further stationssubstantially separated from said casting station and, in said castingstation, a mobile ingot mould comprising two cylindrical, cooled,counter-rotating rolls and two plates each of which is set at the endsof said rolls, to close at the sides of said rolls the space betweenthem, said rolls defining, between their respective facing surfaces, aspace inside which molten metal is cast and solidifies upon contact withthe surface of said rolls and is then extracted from below as a hotmetal strip, and said continuous casting plant further comprising aplurality of further component elements, treatment stations for saidadditional component elements, and moving means for moving each of saidadditional component elements, wherein said treatment stations are allset on the casting plane, said further component elements being movedbetween their respective treatment stations and said casting station byrotating arms located on at least one turret, said turret being set onthe casting plane.
 2. The plant according to claim 1, wherein there areprovided two turrets is located close to one side of the castingstation.
 3. The plant according to claim 1, wherein two additionalturrets are placed adjacent to the casting station, on a plane parallelto the one containing the cast strip.
 4. The plant according to claim 2,wherein said further component elements, moved in casting position byrotating arms comprise a ladle, at least one tundish and/or at least oneunder-tundish or an unloading device, and/or at least one molten metaldistributor within said space between said counter-rotating rolls. 5.The plant according to claim 2, wherein each of said turrets is providedwith two arms, one arm suitable to move said tundish and the other armsuitable to move the under-tundish from their respective treatmentstations, arranged close by to the turrets within the reach of saidarms, and said casting station.
 6. The plant according to claim 3,wherein the additional turrets are provided with robotic arms suitableto move said molten metal distributor nozzle and said lateral platesfrom their respective treatment stations to said casting station.
 7. Theplant according to claim 1, wherein the casting rolls are set in atransversally movable trolley suitable to slide transversally to thecasting direction between a treatment station and said casting station,said trolley being provided with means to place and hold in positionsaid rolls and to adjust the gap between them in order to control thethickness of the cast strip.
 8. The plant according to claim 1, whereinthe casting plane further comprises a tundish rotating turret suitableto put the ladle in casting position, said tundish rotating tower beingpreferably arranged in a central position with respect to the turretsfor moving the tundish and under-tundish.
 9. The plant according toclaim 1, wherein there are provided means for collecting wastes of slagand metal and means for movement thereof.
 10. The plant according toclaim 1, wherein the treatment stations comprise unloading device andplates preheating stations with electric resistances.
 11. The plantaccording to claim 1, wherein the treatment stations-comprise unloadingdevice and plates preheating stations with burners.
 12. The plantaccording to claim 1, wherein the treatment stations comprise unloadingdevice and plates preheating stations with microwaves.